v0.20.0-dev now KometPHP targets PHP 5.3.3 instead of PHP 5.4

- PHP 5.3.3 as minimum requirement instead of 5.4
- System renamed to Environment
- Simplified Environment class
- config loader
- removed environment constants. now you can define yours and initialize
them in a environments.php file like fuelphp
- Listenable converted to class instead of trait (5.3 compat.)